Infrared spectroscopy of 2v4 and v3+2v4 bands of the NO3 radical

The 2v(4) band spectrum of (NO3)-N-14 observed with infrared diode laser spectroscopy was analyzed with the Fourier transform (FT) spectrum in the 760 cm(-1) region, including the Coriolis interaction between v(4) = 2 and v(2) = 1. The vibrational frequencies of v(4) = 2, I = 0, and I = +/- 2 have been determined to be 752.4033(86) and 771.7941(81) cm(-1), respectively. By considering the anharmonic interaction among the 2v(4), v(3), v(4), v(2), and v(2) + 3v(4) states, a relation among the cubic anharmonic constants was obtained as 0.452 Phi(444)zeta(2.4) - 0.271 Phi(344)zeta(2.3) = 127.7 cm(-1). The ratio of transition moments mu(v(2))/mu(2v(4)) was determined to be 0.3 from the perturbation analysis. The second strongest infrared band of (NO3)-N-14, v(3) + 2v(4), observed around 1927 cm(-1) has been analyzed with the hot band v(3) + 2v(4) - v(4) by including the Coriolis interaction with the v(2) = 1, v(4)= 3 state. Similarly, the same band of (NO3)-N-15 was analyzed to give the band origin of 1897.9325(6) cm(-1). The isotope shift 28.2 cm(-1) for the v(3) + 2v(4) vibrational frequency is consistent with a predicted value of 27.3 cm -1. Although there are two A' states in v3 = 1, v4 = 2, only one A(2)(') state has been assigned in the hot band, indicating that the other band has weak intensity. This fact and the strong intensity of the v(3) + 2v(4) band (I-3 = +/- 1, I-4 = 0) are understood as the effect of vibronic interaction. The first-order Coriolis coupling constant zeta of v(3) + 2v(4), l(3) = 1, l(4) = 0 is similar to those of the v(4) and v(3) + v(4) states, and it is concluded that the vibrational Coriolis coupling constant is nearly zero and the observed constants of zeta= -0.19 ((NO3)-N-14) and zeta = -0.15 ((NO3)-N-15) also originate from the effect of vibronic interaction. (C) 2017 Elsevier Inc. All rights reserved.